When to use categories
Categories (along with other features like cross-references, lists, and infoboxes) help readers find information, even if they don't know that it exists or what it's called.
Every page in the article should belong to at least one category. The categories to be included, which serve as classifications, should be the significant (useful) topics to which the subject of the article most closely belongs to as a member, and where readers are most likely to look if they can't remember the name of the thing they are trying to look up. For example:
Article: Elmsley Count Useful category: Cards Not as useful: Category: Counts that start with E
Questions to ask to determine whether it is appropriate to add an article to a category:
- If the category does not already exist, is it possible to write a few paragraphs or more on the subject of the category, explaining it?
- If you go to the article from the category, will it be obvious why the article was put in the category?
- Is the category subject prominently discussed in the article?
If the answer to any of these questions is no, then the category is probably inappropriate. Note that it is always appropriate to add articles to categories that fit into well established taxonomies. For example, every article about a Magician's book is categorized in some category, which is in turn categorized in Category:Books by authors.
Some general guidelines
- Categories are mainly used to browse through similar articles. Make decisions about the structure of categories and subcategories that make it easy for users to browse through similar articles.
- An article will often be in several categories. Restraint should be used as categories become less effective the more there are on any given article.
- Usually, articles should not be in both a category and its subcategory. For example, Golden Gate Bridge is in Category:Suspension bridges, so it should not also be in Category:Bridges. However, there are occasions when this guideline can and should be ignored. For example, Robert Duvall is in Category:Film actors as well as its subcategory Category:Best Actor Academy Award winners.
- Check to see where siblings of the article reside. If there are few if any articles in a category, the article probably belongs in one of the subcategories.
- Articles should be placed in categories with the same name. However, the article and the category do not have to be categorized the same way. The article can also be placed in categories populated with similar articles.
- There are often occasions when articles might ideally be moved from a category to two or more of its subcategories, but not all of the subcategories exist. In such cases consider creating the additional subcategories, but if you decide not to do so, leave the articles in the parent category for the time being.
- An article should normally possess all the referenced information necessary to demonstrate that it belongs in each of its categories. Avoid including categories in an article if the article itself doesn't adequately show it belongs there. For example, avoid placing a category for a profession or award unless the article provides some verification that the placement is accurate. Use the Template:Category unsourced tag if the article is in a category but no sources demonstrate the category is appropriate.
- Generally, the relationship between an article and its categories should be definable as "(Article) is (category)": John Goodman is an American actor, Copenhagen is a city in Denmark, Jane Austen is an English writer, etc. Do not apply categories whose relationship to the topic is definable only as "(Article) is a subject related to (category)", such as filing a teacher directly into Category:Education, an album directly into Category:Music or a book about skydiving directly into Category:Parachuting.
- If you don't know where to put an article, don't worry about it.